With my "virtual" dojo program, I often have to advise students how to use certain programs and features of the program. If they have Windows 7, I can now use this program. . .
In Windows 7, choose Help and Support, More Support Options, and select Remote Assistance at the bottom of the window. Once you've fired up Remote Assistance, it's time to send the help invitation. In Windows 7, the invitation can be sent as an e-mail. The credentials that will actually let a remote computer connect with yours will be attached to the e-mail. For further security, the user will also need to create a password that the remote user will need to enter before they're granted full access.
As long as Remote Assistance is connected on both sides, the local user will be able to watch their desktop, seeing everything that's going on. It's a great way to teach someone how to fix their broken computer when you can't physically be there.